is the creator of the title graphic for my site!
Case 01: Cover
Sent by Andy, this picture shows many Sega CD (the name of the Mega CD in the USA) games. Looking at the picture carefully, it becomes blatantly obvious that the Sonic CD cover shown isn't the final one.
Case 02: Title Screen
Above is a picture of the Sonic CD title screen, sent by ^Luck^. Wait a minute! That isn't the the final Sonic CD title screen. The most obvious difference is the name 'CD Sonic', but there are still quite a few more differences.
Case 3 : Wierd Enemy
This picture of Sonic CD beta at first glance doesn't seem too different but if you look closely you'll notice it has a few very interesting differences. The first and most obvious difference you'll notice is the strange claws on Robitnik's machine instead of bumpers. Also the strange stars in are nowhere to be seen in the final. It all kind of makes you wonder what other little cosmetic changes SEGA put in before they released the final.
Case 4 : Sonic 2 Levels in Sonic CD
John Parker wrote
this little tidbit about sonic CD..
Of course this is all just a theory but I have to say it makes a lot more sense than just dropping the levels. Kudos to John for finding this.